I bought a used bike with this fork. Took it out for its first long ride, and when I got home I noticed some grease had seeped out of the pre-load knob on the spring side of the fork. When I take it out in front of the house and compress the fork a few times I am getting a hissing sound. Is this as easy as an o-ring to fix it, do I need a new top cap, thoughts?

Thanks